User Equipment with Improved Tune-Away Performance During Measurement

ABSTRACT

Operating a user equipment (UE) which comprises a first radio that is configured to operate according to a first radio access technology (RAT) and a second RAT. The UE may receive a request to perform a tune away operation for the second RAT while performing measurement for the first RAT (e.g., intra-cell measurement, inter-cell measurement, and/or inter-RAT measurement). Instead of waiting to complete the measurement of the first RAT, the UE may tune the radio to a frequency of the second RAT to perform the tune away operation (e.g., page decoding) for the second RAT. After completing the tune away operation of the second RAT, the UE may tune the radio back to a frequency corresponding to the first RAT in order to continue the measurement operations of the first RAT.

PRIORITY INFORMATION

The present application is a continuation of U.S. patent applicationSer. No. 14/956,923, which was filed on Dec. 2, 2015, titled “UserEquipment with Improved Tune-Away Performance During Measurement”, whoseinventor is Li Su, which was a continuation of U.S. patent applicationSer. No. 14/254,087, which was filed on Apr. 16, 2014, titled “UserEquipment with Improved Tune-Away Performance During Measurement”, whoseinventor is Li Su, which claims benefit of priority of U.S. ProvisionalApplication Ser. No. 61/948,834, titled “User Equipment with ImprovedTune-Away Performance During Measurement”, whose inventor is Li Su,which was filed on Mar. 6, 2014, all of which are hereby incorporated byreference in their entirety as though fully and completely set forthherein.

FIELD OF THE INVENTION

The present application relates to wireless devices, and moreparticularly to a system and method for providing improved performanceand/or reduced power consumption in wireless devices that supportmultiple radio access technologies (RATs).

DESCRIPTION OF THE RELATED ART

Wireless communication systems are rapidly growing in usage. Further,wireless communication technology has evolved from voice-onlycommunications to also include the transmission of data, such asInternet and multimedia content. Therefore, improvements are desired inwireless communication. In particular, the large amount of functionalitypresent in a user equipment (UE), e.g., a wireless device such as acellular phone, can place a significant strain on the battery life ofthe UE. Further, where a UE is configured to support multiple radioaccess technologies (RATs), certain performance degradations can occuron one or more of the RATs, such as due to tune-away operations of theother RAT. As a result, techniques are desired which provide powersavings and/or improved performance in such wireless UE devices.

New and improved cellular radio access technologies (RATs) are sometimesdeployed in addition to existing RATs. For example, networksimplementing Long Term Evolution (LTE) technology, developed andstandardized by the Third Generation Partnership Project (3GPP), arecurrently being deployed. LTE and other newer RATs often support fasterdata rates than networks utilizing legacy RATs, such as various secondgeneration (2G) and third generation (3G) RATs.

However, in some deployments, LTE and other new RATs may not fullysupport some services that can be handled by legacy networks.Accordingly, LTE networks are often co-deployed in overlapping regionswith legacy networks and UE devices may transition between RATs asservices or coverage may require. For example, in some deployments, LTEnetworks are not capable of supporting voice calls. Thus, for examplewhen a UE device receives or initiates a circuit switched voice callwhile connected to an LTE network that does not support voice calls, theUE device can transition to a legacy network, such as one which uses aGSM (Global System for Mobile Communications) RAT or a “1×” (CodeDivision Multiple Access 2000 (CDMA2000) 1×) RAT that supports voicecalls, among other possibilities.

Some UE devices use a single radio to support operation on multiplecellular RATs. For example, some UE devices use a single radio tosupport operation on both LTE and GSM networks. The use of a singleradio for multiple RATs makes transitioning between networks, such as inresponse to a page message for an incoming voice call or circuitswitched service, more complex. In addition, the use of a single radiofor multiple RATs presents certain power usage and performance issues.

For example, in such systems the UE may periodically tune from the firstnetwork, using a more advanced RAT, to the second network, using alegacy RAT, e.g., to listen to a paging channel for a voice call.However, such tune-away operations from a more advanced RAT, such asLTE, to a legacy RAT, such as GSM, can result in increased powerconsumption and/or performance degradation of the LTE network.

Therefore, it would be desirable to provide improved performance andpower consumption in wireless communication systems where a UE devicesuse a single radio to support operation on multiple cellular RATs.

SUMMARY OF THE INVENTION

Embodiments described herein relate to a User Equipment (UE) device andassociated method for operating a user equipment (UE) that includes afirst radio that is configured to operate according to a first radioaccess technology (RAT) and a second RAT. The UE may receive a requestto perform a tune away operation for the second RAT while performingmeasurement for the first RAT (e.g., intra-cell measurement, inter-cellmeasurement, and/or inter-RAT measurement). Instead of waiting tocomplete the measurement of the first RAT, the UE may tune the radio toa frequency of the second RAT to perform the tune away operation (e.g.,page decoding) for the second RAT. After completing the tune awayoperation of the second RAT, the UE may tune the radio back to afrequency corresponding to the first RAT in order to continue themeasurement operations of the first RAT.

Embodiments described herein relate to a User Equipment (UE) device andassociated method for performing a tune away operation for a second RATwhile performing warm up operations for a first RAT. For example, whilethe UE is waking up from a sleep mode to perform communication using thefirst RAT, it may perform various actions, such as warming up a crystaloscillator, performing start-up operations for one or more processors,and/or performing time tracking loop and/or frequency tracking loop(TTL/FTL) operations to synchronize operations with a base station ofthe first RAT. However, a tune away request may be received during thiswaking up process. If the tune away request is received prior to theTTL/FTL operations, then it may be performed just prior to the TTL/FTLoperations. After the tune away procedure for the second RAT completes,the TTL/FTL operations of the first RAT may be performed. If the tuneaway request is received during the TTL/FTL operations, then they may becancelled in order to perform the tune away operation for the secondRAT. After completion, the TTL/FTL operations may be performed for thefirst RAT.

This Summary is provided for purposes of summarizing some exemplaryembodiments to provide a basic understanding of aspects of the subjectmatter described herein. Accordingly, the above-described features aremerely examples and should not be construed to narrow the scope orspirit of the subject matter described herein in any way. Otherfeatures, aspects, and advantages of the subject matter described hereinwill become apparent from the following Detailed Description, Figures,and Claims.

BRIEF DESCRIPTION OF THE DRAWINGS

A better understanding of the present invention can be obtained when thefollowing detailed description of the embodiments is considered inconjunction with the following drawings.

FIG. 1 illustrates an example user equipment (UE) according to oneembodiment;

FIG. 2 illustrates an example wireless communication system where a UEcommunicates with two base stations using two different RATs;

FIG. 3 is an example block diagram of a base station, according to oneembodiment;

FIG. 4 is an example block diagram of a UE, according to one embodiment;

FIGS. 5A and 5B are example block diagrams of wireless communicationcircuitry in the UE, according to one embodiment;

FIG. 6 is a flowchart diagram illustrating an exemplary method forresolving conflict between tune aways of a first and second RAT;

FIGS. 7A and 7B are diagrams corresponding to embodiments of the methodof FIG. 6;

FIG. 8 is a flowchart diagram illustrating an exemplary method forresolving conflict between tune aways of a first and second RAT;

FIGS. 9A and 9B are diagrams corresponding to embodiments of the methodof FIG. 8;

FIG. 10 is a flowchart diagram illustrating an exemplary method forinserting tune away of a second RAT in Intra-Cell Measurement for aFirst RAT;

FIGS. 11A and 11B are diagrams corresponding to embodiments of themethod of FIG. 10;

FIG. 12 is a flowchart diagram illustrating an exemplary method forinserting tune away of a second RAT in Inter-Cell and/or Inter-RATMeasurement for a First RAT;

FIGS. 13A and 13B are diagrams corresponding to embodiments of themethod of FIG. 12; and

FIG. 14 is a flowchart diagram illustrating an exemplary method forinserting tune away of a second RAT during Warm Up of a First RAT.

While the invention is susceptible to various modifications andalternative forms, specific embodiments thereof are shown by way ofexample in the drawings and are herein described in detail. It should beunderstood, however, that the drawings and detailed description theretoare not intended to limit the invention to the particular formdisclosed, but on the contrary, the intention is to cover allmodifications, equivalents and alternatives falling within the spiritand scope of the present invention as defined by the appended claims.

DETAILED DESCRIPTION OF THE EMBODIMENTS Acronyms

The following acronyms are used in the present disclosure.

3GPP: Third Generation Partnership Project

3GPP2: Third Generation Partnership Project 2

GSM: Global System for Mobile Communications

UMTS: Universal Mobile Telecommunications System

LTE: Long Term Evolution

RAT: Radio Access Technology

TX: Transmit

RX: Receive

TERMS

The following is a glossary of terms used in the present application:

Memory Medium—Any of various types of memory devices or storage devices.The term “memory medium” is intended to include an installation medium,e.g., a CD-ROM, floppy disks, or tape device; a computer system memoryor random access memory such as DRAM, DDR RAM, SRAM, EDO RAM, RambusRAM, etc.; a nonvolatile memory such as a Flash, magnetic media, e.g., ahard drive, or optical storage; registers, or other similar types ofmemory elements, etc. The memory medium may include other types ofmemory as well or combinations thereof. In addition, the memory mediummay be located in a first computer system in which the programs areexecuted, or may be located in a second different computer system whichconnects to the first computer system over a network, such as theInternet. In the latter instance, the second computer system may provideprogram instructions to the first computer for execution. The term“memory medium” may include two or more memory mediums which may residein different locations, e.g., in different computer systems that areconnected over a network. The memory medium may store programinstructions (e.g., embodied as computer programs) that may be executedby one or more processors.

Carrier Medium—a memory medium as described above, as well as a physicaltransmission medium, such as a bus, network, and/or other physicaltransmission medium that conveys signals such as electrical,electromagnetic, or digital signals.

Programmable Hardware Element—includes various hardware devicescomprising multiple programmable function blocks connected via aprogrammable interconnect. Examples include FPGAs (Field ProgrammableGate Arrays), PLDs (Programmable Logic Devices), FPOAs (FieldProgrammable Object Arrays), and CPLDs (Complex PLDs). The programmablefunction blocks may range from fine grained (combinatorial logic or lookup tables) to coarse grained (arithmetic logic units or processorcores). A programmable hardware element may also be referred to as“reconfigurable logic”.

Computer System—any of various types of computing or processing systems,including a personal computer system (PC), mainframe computer system,workstation, network appliance, Internet appliance, personal digitalassistant (PDA), personal communication device, smart phone, televisionsystem, grid computing system, or other device or combinations ofdevices. In general, the term “computer system” can be broadly definedto encompass any device (or combination of devices) having at least oneprocessor that executes instructions from a memory medium.

User Equipment (UE) (or “UE Device”)—any of various types of computersystems devices which are mobile or portable and which performs wirelesscommunications. Examples of UE devices include mobile telephones orsmart phones (e.g., iPhone™, Android™-based phones), portable gamingdevices (e.g., Nintendo DS™, PlayStation Portable™, Gameboy Advance™,iPhone™), laptops, PDAs, portable Internet devices, music players, datastorage devices, other handheld devices, as well as wearable devicessuch as wrist-watches, headphones, pendants, earpieces, etc. In general,the term “UE” or “UE device” can be broadly defined to encompass anyelectronic, computing, and/or telecommunications device (or combinationof devices) which is easily transported by a user and capable ofwireless communication.

Base Station—The term “Base Station” has the full breadth of itsordinary meaning, and at least includes a wireless communication stationinstalled at a fixed location and used to communicate as part of awireless telephone system or radio system.

Processing Element—refers to various elements or combinations ofelements. Processing elements include, for example, circuits such as anASIC (Application Specific Integrated Circuit), portions or circuits ofindividual processor cores, entire processor cores, individualprocessors, programmable hardware devices such as a field programmablegate array (FPGA), and/or larger portions of systems that includemultiple processors.

Automatically—refers to an action or operation performed by a computersystem (e.g., software executed by the computer system) or device (e.g.,circuitry, programmable hardware elements, ASICs, etc.), without userinput directly specifying or performing the action or operation. Thusthe term “automatically” is in contrast to an operation being manuallyperformed or specified by the user, where the user provides input todirectly perform the operation. An automatic procedure may be initiatedby input provided by the user, but the subsequent actions that areperformed “automatically” are not specified by the user, i.e., are notperformed “manually”, where the user specifies each action to perform.For example, a user filling out an electronic form by selecting eachfield and providing input specifying information (e.g., by typinginformation, selecting check boxes, radio selections, etc.) is fillingout the form manually, even though the computer system must update theform in response to the user actions. The form may be automaticallyfilled out by the computer system where the computer system (e.g.,software executing on the computer system) analyzes the fields of theform and fills in the form without any user input specifying the answersto the fields. As indicated above, the user may invoke the automaticfilling of the form, but is not involved in the actual filling of theform (e.g., the user is not manually specifying answers to fields butrather they are being automatically completed). The presentspecification provides various examples of operations beingautomatically performed in response to actions the user has taken.

FIG. 1—User Equipment

FIG. 1 illustrates an example user equipment (UE) 106 according to oneembodiment. The term UE 106 may be any of various devices as definedabove. UE device 106 may include a housing 12 which may be constructedfrom any of various materials. UE 106 may have a display 14, which maybe a touch screen that incorporates capacitive touch electrodes. Display14 may be based on any of various display technologies. The housing 12of the UE 106 may contain or comprise openings for any of variouselements, such as home button 16, speaker port 18, and other elements(not shown), such as microphone, data port, and possibly various othertypes of buttons, e.g., volume buttons, ringer button, etc.

The UE 106 may support multiple radio access technologies (RATs). Forexample, UE 106 may be configured to communicate using any of variousRATs such as two or more of Global System for Mobile Communications(GSM), Universal Mobile Telecommunications System (UMTS), Code DivisionMultiple Access (CDMA) (e.g., CDMA2000 1×RTT or other CDMA radio accesstechnologies), Long Term Evolution (LTE), Advanced LTE, and/or otherRATs. For example, the UE 106 may support at least two radio accesstechnologies such as LTE and GSM. Various different or other RATs may besupported as desired.

The UE 106 may comprise one or more antennas. The UE 106 may alsocomprise any of various radio configurations, such as variouscombinations of one or more transmitter chains (TX chains) and one ormore receiver chains (RX chains). For example, the UE 106 may comprise aradio that supports two or more RATs. The radio may comprise a single TX(transmit) chain and a single RX (receive) chain. Alternatively, theradio may comprise a single TX chain and two RX chains, e.g., thatoperate on the same frequency. In another embodiment, the UE 106comprises two or more radios, i.e., two or more TX/RX chains (two ormore TX chains and two or more RX chains).

In the embodiment described herein, the UE 106 comprises two antennaswhich communicate using two or more RATs. For example, the UE 106 mayhave a pair of cellular telephone antennas coupled to a single radio orshared radio. The antennas may be coupled to the shared radio (sharedwireless communication circuitry) using switching circuits and otherradio-frequency front-end circuitry. For example, the UE 106 may have afirst antenna that is coupled to a transceiver or radio, i.e., a firstantenna that is coupled to a transmitter chain (TX chain) fortransmission and which is coupled to a first receiver chain (RX chain)for receiving. The UE 106 may also comprise a second antenna that iscoupled to a second RX chain. The first and second receiver chains mayshare a common local oscillator, which means that both of the first andsecond receiver chains tune to the same frequency. The first and secondreceiver chains may be referred to as the primary receiver chain (PRX)and the diversity receiver chain (DRX).

In one embodiment, the PRX and DRX receiver chains operate as a pair andtime multiplex among two or more RATs, such as LTE and one or more otherRATs such as GSM or CDMA1×. In the primary embodiment described hereinthe UE 106 comprises one transmitter chain and two receiver chains (PRXand DRX), wherein the transmitter chain and the two receiver chains(acting as a pair) time multiplex between two (or more) RATs, such asLTE and GSM.

Each antenna may receive a wide range of frequencies such as from 600MHz up to 3 GHz. Thus, for example, the local oscillator of the PRX andDRX receiver chains may tune to a specific frequency such as an LTEfrequency band, where the PRX receiver chain receives samples fromantenna 1 and the DRX receiver chain receives samples from antenna 2,both on the same frequency (since they use the same local oscillator).The wireless circuitry in the UE 106 can be configured in real timedepending on the desired mode of operation for the UE 106. In theexample embodiment described herein, the UE 106 is configured to supportLTE and GSM radio access technologies.

FIG. 2—Communication System

FIG. 2 illustrates an exemplary (and simplified) wireless communicationsystem. It is noted that the system of FIG. 2 is merely one example of apossible system, and embodiments may be implemented in any of varioussystems, as desired.

As shown, the exemplary wireless communication system includes basestations 102A and 102B which communicate over a transmission medium withone or more user equipment (UE) devices, represented as UE 106. The basestations 102 may be base transceiver stations (BTS) or cell sites, andmay include hardware that enables wireless communication with the UE106. Each base station 102 may also be equipped to communicate with acore network 100. For example, base station 102A may be coupled to corenetwork 100A, while base station 102B may be coupled to core network100B. Each core network may be operated by a respective cellular serviceprovider, or the plurality of core networks 100A may be operated by thesame cellular service provider. Each core network 100 may also becoupled to one or more external networks (such as external network 108),which may include the Internet, a Public Switched Telephone Network(PSTN), and/or any other network. Thus, the base stations 102 mayfacilitate communication between the UE devices 106 and/or between theUE devices 106 and the networks 100A, 100B, and 108.

The base stations 102 and the UEs 106 may be configured to communicateover the transmission medium using any of various radio accesstechnologies (“RATs”, also referred to as wireless communicationtechnologies or telecommunication standards), such as GSM, UMTS (WCDMA),LTE, LTE Advanced (LTE-A), 3GPP2 CDMA2000 (e.g., 1×RTT, 1×EV-DO, HRPD,eHRPD), IEEE 802.11 (WLAN or Wi-Fi), IEEE 802.16 (WiMAX), etc.

Base station 102A and core network 100A may operate according to a firstRAT (e.g., LTE) while base station 102B and core network 100B mayoperate according to a second (e.g., different) RAT (e.g., GSM, CDMA2000 or other legacy or circuit switched technologies). The two networksmay be controlled by the same network operator (e.g., cellular serviceprovider or “carrier”), or by different network operators, as desired.In addition, the two networks may be operated independently of oneanother (e.g., if they operate according to different RATs), or may beoperated in a somewhat coupled or tightly coupled manner.

Note also that while two different networks may be used to support twodifferent RATs, such as illustrated in the exemplary networkconfiguration shown in FIG. 2, other network configurations implementingmultiple RATs are also possible. As one example, base stations 102A and102B might operate according to different RATs but couple to the samecore network. As another example, multi-mode base stations capable ofsimultaneously supporting different RATs (e.g., LTE and GSM, LTE andCDMA2000 1×RTT, and/or any other combination of RATs) might be coupledto a core network that also supports the different cellularcommunication technologies. In one embodiment, the UE 106 may beconfigured to use a first RAT that is a packet-switched technology(e.g., LTE) and a second RAT that is a circuit-switched technology(e.g., GSM or 1×RTT).

As discussed above, UE 106 may be capable of communicating usingmultiple RATs, such as those within 3GPP, 3GPP2, or any desired cellularstandards. The UE 106 might also be configured to communicate usingWLAN, Bluetooth, one or more global navigational satellite systems(GNSS, e.g., GPS or GLONASS), one and/or more mobile televisionbroadcasting standards (e.g., ATSC-M/H or DVB-H), etc. Othercombinations of network communication standards are also possible.

Base stations 102A and 102B and other base stations operating accordingto the same or different RATs or cellular communication standards maythus be provided as a network of cells, which may provide continuous ornearly continuous overlapping service to UE 106 and similar devices overa wide geographic area via one or more radio access technologies (RATs).

FIG. 3—Base Station

FIG. 3 illustrates an exemplary block diagram of a base station 102. Itis noted that the base station of FIG. 3 is merely one example of apossible base station. As shown, the base station 102 may includeprocessor(s) 504 which may execute program instructions for the basestation 102. The processor(s) 504 may also be coupled to memorymanagement unit (MMU) 540, which may be configured to receive addressesfrom the processor(s) 504 and translate those addresses to locations inmemory (e.g., memory 560 and read only memory (ROM) 550) or to othercircuits or devices.

The base station 102 may include at least one network port 570. Thenetwork port 570 may be configured to couple to a telephone network andprovide a plurality of devices, such as UE devices 106, access to thetelephone network as described above.

The network port 570 (or an additional network port) may also oralternatively be configured to couple to a cellular network, e.g., acore network of a cellular service provider. The core network mayprovide mobility related services and/or other services to a pluralityof devices, such as UE devices 106. In some cases, the network port 570may couple to a telephone network via the core network, and/or the corenetwork may provide a telephone network (e.g., among other UE devices106 serviced by the cellular service provider).

The base station 102 may include at least one antenna 534. The at leastone antenna 534 may be configured to operate as a wireless transceiverand may be further configured to communicate with UE devices 106 viaradio 530. The antenna 534 communicates with the radio 530 viacommunication chain 532. Communication chain 532 may be a receive chain,a transmit chain or both. The radio 530 may be configured to communicatevia various RATs, including, but not limited to, LTE, GSM, WCDMA,CDMA2000, etc.

The processor(s) 504 of the base station 102 may be configured toimplement part or all of the methods described herein, e.g., byexecuting program instructions stored on a memory medium (e.g., anon-transitory computer-readable memory medium). Alternatively, theprocessor 504 may be configured as a programmable hardware element, suchas an FPGA (Field Programmable Gate Array), or as an ASIC (ApplicationSpecific Integrated Circuit), or a combination thereof.

FIG. 4—User Equipment (UE)

FIG. 4 illustrates an example simplified block diagram of a UE 106. Asshown, the UE 106 may include a system on chip (SOC) 400, which mayinclude portions for various purposes. The SOC 400 may be coupled tovarious other circuits of the UE 106. For example, the UE 106 mayinclude various types of memory (e.g., including NAND flash 410), aconnector interface 420 (e.g., for coupling to a computer system, dock,charging station, etc.), the display 460, cellular communicationcircuitry 430 such as for LTE, GSM, etc., and short range wirelesscommunication circuitry 429 (e.g., Bluetooth and WLAN circuitry). The UE106 may further comprise one or more smart cards 310 that comprise SIM(Subscriber Identity Module) functionality, such as one or more UICC(s)(Universal Integrated Circuit Card(s)) cards 310. The cellularcommunication circuitry 430 may couple to one or more antennas,preferably two antennas 435 and 436 as shown. The short range wirelesscommunication circuitry 429 may also couple to one or both of theantennas 435 and 436 (this connectivity is not shown for ease ofillustration).

As shown, the SOC 400 may include processor(s) 402 which may executeprogram instructions for the UE 106 and display circuitry 404 which mayperform graphics processing and provide display signals to the display460. The processor(s) 402 may also be coupled to memory management unit(MMU) 440, which may be configured to receive addresses from theprocessor(s) 402 and translate those addresses to locations in memory(e.g., memory 406, read only memory (ROM) 450, NAND flash memory 410)and/or to other circuits or devices, such as the display circuitry 404,cellular communication circuitry 430, short range wireless communicationcircuitry 429, connector I/F 420, and/or display 460. The MMU 440 may beconfigured to perform memory protection and page table translation orset up. In some embodiments, the MMU 440 may be included as a portion ofthe processor(s) 402.

In one embodiment, as noted above, the UE 106 comprises at least onesmart card 310, such as a UICC 310, which executes one or moreSubscriber Identity Module (SIM) applications and/or otherwise implementSIM functionality. The at least one smart card 310 may be only a singlesmart card 310, or the UE 106 may comprise two or more smart cards 310.Each smart card 310 may be embedded, e.g., may be soldered onto acircuit board in the UE 106, or each smart card 310 may be implementedas a removable smart card. Thus the smart card(s) 310 may be one or moreremovable smart cards (such as UICC cards, which are sometimes referredto as “SIM cards”), and/or the smart card(s) 310 may be one or moreembedded cards (such as embedded UICCs (eUICCs), which are sometimesreferred to as “eSIMs” or “eSIM cards”). In some embodiments (such aswhen the smart card(s) 310 include an eUICC), one or more of the smartcard(s) 310 may implement embedded SIM (eSIM) functionality; in such anembodiment, a single one of the smart card(s) 310 may execute multipleSIM applications. Each of the smart card(s) 310 may include componentssuch as a processor and a memory; instructions for performing SIM/eSIMfunctionality may be stored in the memory and executed by the processor.In one embodiment, the UE 106 may comprise a combination of removablesmart cards and fixed/non-removable smart cards (such as one or moreeUICC cards that implement eSIM functionality), as desired. For example,the UE 106 may comprise two embedded smart cards 310, two removablesmart cards 310, or a combination of one embedded smart card 310 and oneremovable smart card 310. Various other SIM configurations are alsocontemplated.

As noted above, in one embodiment, the UE 106 comprises two or moresmart cards 310, each implementing SIM functionality. The inclusion oftwo or more SIM smart cards 310 in the UE 106 may allow the UE 106 tosupport two different telephone numbers and may allow the UE 106 tocommunicate on corresponding two or more respective networks. Forexample, a first smart card 310 may comprise SIM functionality tosupport a first RAT such as LTE, and a second smart card 310 maycomprise SIM functionality to support a second RAT such as GSM. Otherimplementations and RATs are of course possible. Where the UE 106comprises two smart cards 310, the UE 106 may support Dual SIM DualActive (DSDA) functionality. The DSDA functionality may allow the UE 106to be simultaneously connected to two networks (and use two differentRATs) at the same time. The DSDA functionality may also allow the UE 106may to simultaneously receive voice calls or data traffic on eitherphone number. In another embodiment, the UE 106 supports Dual SIM DualStandby (DSDS) functionality. The DSDS functionality may allow either ofthe two smart cards 310 in the UE 106 to be on standby waiting for avoice call and/or data connection. In DSDS, when a call/data isestablished on one SIM 310, the other SIM 310 is no longer active. Inone embodiment, DSDx functionality (either DSDA or DSDS functionality)may be implemented with a single smart card (e.g., a eUICC) thatexecutes multiple SIM applications for different carriers and/or RATs.

As noted above, the UE 106 may be configured to communicate wirelesslyusing multiple radio access technologies (RATs). As further noted above,in such instances, the cellular communication circuitry (radio(s)) 430may include radio components which are shared between multiple RATSand/or radio components which are configured exclusively for useaccording to a single RAT. Where the UE 106 comprises at least twoantennas, the antennas 435 and 436 may be configurable for implementingMIMO (multiple input multiple output) communication.

As described herein, the UE 106 may include hardware and softwarecomponents for implementing features for communicating using two or moreRATs, such as those described herein. The processor 402 of the UE device106 may be configured to implement part or all of the features describedherein, e.g., by executing program instructions stored on a memorymedium (e.g., a non-transitory computer-readable memory medium).Alternatively (or in addition), processor 402 may be configured as aprogrammable hardware element, such as an FPGA (Field Programmable GateArray), or as an ASIC (Application Specific Integrated Circuit).Alternatively (or in addition) the processor 402 of the UE device 106,in conjunction with one or more of the other components 400, 404, 406,410, 420, 430, 435, 440, 450, 460 may be configured to implement part orall of the features described herein.

FIGS. 5A and 5B—UE Transmit/Receive Logic

FIG. 5A illustrates a portion of UE 106 according to one embodiment. Asshown, UE 106 may comprise control circuitry 42 that is configured tostore and execute control code for implementing control algorithms inthe UE 106. Control circuitry 42 may include storage and processingcircuitry 28 (e.g., a microprocessor, memory circuits, etc.) and mayinclude baseband processor integrated circuit 58. Baseband processor 58may form part of wireless circuitry 34 and may include memory andprocessing circuits (i.e., baseband processor 58 may be considered toform part of the storage and processing circuitry of UE 106). Basebandprocessor 58 may comprise software and/or logic for handling variousdifferent RATs, such as GSM logic 72 and LTE logic 74, among others.

Baseband processor 58 may provide data to storage and processingcircuitry 28 (e.g., a microprocessor, nonvolatile memory, volatilememory, other control circuits, etc.) via path 48. The data on path 48may include raw and processed data associated with UE cellularcommunications and operations, such as cellular communication data,wireless (antenna) performance metrics for received signals, informationrelated to tune-away operations, information related to pagingoperations, etc. This information may be analyzed by storage andprocessing circuitry 28 and/or processor 58 and, in response, storageand processing circuitry 28 (or, if desired, baseband processor 58) mayissue control commands for controlling wireless circuitry 34. Forexample, storage and processing circuitry 28 may issue control commandson path 52 and path 50 and/or baseband processor 58 may issue commandson path 46 and path 51.

Wireless circuitry 34 may include radio-frequency transceiver circuitrysuch as radio-frequency transceiver circuitry 60 and radio-frequencyfront-end circuitry 62. Radio-frequency transceiver circuitry 60 mayinclude one or more radio-frequency transceivers. In the embodimentshown radio-frequency transceiver circuitry 60 comprises transceiver(TX) chain 59, receiver (RX) chain 61 and RX chain 63. As noted above,the two RX chains 61 and 63 may be a primary RX chain 61 and a diversityRX chain 63. The two RX chains 61 and 63 may be connected to the samelocal oscillator (LO) and thus may operate together at the samefrequency for MIMO operations. Thus the TX chain 59 and the two RXchains 61 and 63 may be considered, along with other necessarycircuitry, as a single radio. Other embodiments are of coursecontemplated. For example, the radio-frequency transceiver circuitry 60may comprise only a single TX chain and only a single RX chain, also asingle radio embodiment. Thus the term “radio” may be defined to havethe broadest scope of its ordinary and accepted meaning, and comprisesthe circuitry normally found in a radio, including either a single TXchain and a single RX chain or a single TX chain and two (or more) RXchains, e.g., connected to the same LO. The term radio may encompass thetransmit and receive chains discussed above and may also include digitalsignal processing coupled to the radio frequency circuitry (e.g., thetransmit and receive chains) associated with performing wirelesscommunication. As one example, the transmit chain may include suchcomponents as amplifier, mixer, filter, and digital analog converter.Similarly, the receive chain(s) may include, e.g., such components asamplifier, mixer, filter, and analog to digital converter. As mentionedabove, multiple receive chains may share a LO, although in otherembodiments, they may comprise their own LO. Wireless communicationcircuitry may encompass a larger set of components, e.g., including oneor more radios of the UE (transmit/receive chains and/or digital signalprocessing), baseband processors, etc. The term “cellular wirelesscommunication circuitry” includes various circuitry for performingcellular communication, e.g., as opposed to other protocols that are notcellular in nature, such as Bluetooth. Certain embodiments of theinvention described herein may operate to improve performance when asingle radio (i.e., a radio with a single TX chain and single RX chain;or a radio with a single TX chain and two RX chains, where the two RXchains are connected to the same LO) supports multiple RATs.

As shown in FIG. 5B, the radio-frequency transceiver circuitry 60 mayalso comprise two or more TX chains and two or more RX chains. Forexample, FIG. 5B shows an embodiment with a first radio 57 comprising TXchain 59 and RX chain 61 and a second radio 63 comprising a first TXchain 65 and a second TX chain 67. Embodiments are also contemplatedwhere additional TX/RX receive chains may be included in the embodimentof FIG. 5A, i.e., in addition to the one TX chain 59 and two RX chains61 and 63 shown. In these embodiments that have multiple TX and RXchains, when only one radio is currently active, e.g., the second radiois turned off to save power, certain embodiments of the inventiondescribed herein may operate to improve performance of the single activeradio when it supports multiple RATs.

Baseband processor 58 may receive digital data that is to be transmittedfrom storage and processing circuitry 28 and may use path 46 andradio-frequency transceiver circuitry 60 to transmit correspondingradio-frequency signals. Radio-frequency front end 62 may be coupledbetween radio-frequency transceiver 60 and antennas 40 and may be usedto convey the radio-frequency signals that are produced byradio-frequency transceiver circuitry 60 to antennas 40. Radio-frequencyfront end 62 may include radio-frequency switches, impedance matchingcircuits, filters, and other circuitry for forming an interface betweenantennas 40 and radio-frequency transceiver 60.

Incoming radio-frequency signals that are received by antennas 40 may beprovided to baseband processor 58 via radio-frequency front end 62,paths such as paths 54 and 56, receiver circuitry in radio-frequencytransceiver 60, and paths such as path 46. Path 54 may, for example, beused in handling signals associated with transceiver 57, whereas path 56may be used in handling signals associated with transceiver 63. Basebandprocessor 58 may convert received signals into digital data that isprovided to storage and processing circuitry 28. Baseband processor 58may also extract information from received signals that is indicative ofsignal quality for the channel to which the transceiver is currentlytuned. For example, baseband processor 58 and/or other circuitry incontrol circuitry 42 may analyze received signals to produce variousmeasurements, such as bit error rate measurements, measurements on theamount of power associated with incoming wireless signals, strengthindicator (RSSI) information, received signal code power (RSCP)information, reference symbol received power (RSRP) information,signal-to-interference ratio (SINR) information, signal-to-noise ratio(SNR) information, channel quality measurements based on signal qualitydata such as Ec/Io or Ec/No data, etc.

Radio-frequency front end 62 may include switching circuitry. Theswitching circuitry may be configured by control signals received fromcontrol circuitry 42 (e.g., control signals from storage and processingcircuitry 28 via path 50 and/or control signals from baseband processor58 via path 51). The switching circuitry may include a switch (switchcircuit) that is used to connect TX and RX chain(s) to antennas 40A and40B. Radio-frequency transceiver circuitry 60 may be configured bycontrol signals received from storage and processing circuitry over path52 and/or control signals received from baseband processor 58 over path46.

The number of antennas that are used may depend on the operating modefor UE 106. For example, as shown in FIG. 5A, in normal LTE operations,antennas 40A and 40B may be used with respective receivers 61 and 63 toimplement a receive diversity scheme, such as for MIMO operations. Withthis type of arrangement, two LTE data streams may be simultaneouslyreceived and processed using baseband processor 58. When it is desiredto monitor a GSM paging channel for incoming GSM pages, one or both ofthe antennas may be temporarily used in receiving GSM paging channelsignals.

Control circuitry 42 may be used to execute software for handling morethan one radio access technology. For example, baseband processor 58 mayinclude memory and control circuitry for implementing multiple protocolstacks such as a GSM protocol stack 72 and an LTE protocol stack 74.Thus, protocol stack 72 may be associated with a first radio accesstechnology such as GSM (as an example), and protocol stack 74 may beassociated with a second radio access technology such as LTE (as anexample). During operation, UE 106 may use GSM protocol stack 72 tohandle GSM functions and may use LTE protocol stack 74 to handle LTEfunctions. Additional protocol stacks, additional transceivers,additional antennas 40, and other additional hardware and/or softwaremay be used in UE 106 if desired. The arrangement of FIGS. 5A and 5B ismerely illustrative. In one embodiment, one or both of the protocolstacks may be configured to implement the methods described in theflowcharts below.

In one embodiment of FIG. 5A (or 5B), the cost and complexity of UE 106may be minimized by implementing the wireless circuitry of FIG. 5A (or5B) using an arrangement in which baseband processor 58 andradio-transceiver circuitry 60 are used to support both LTE and GSMtraffic.

The GSM radio access technology may generally be used to carry voicetraffic, whereas the LTE radio access technology may generally be usedto carry data traffic. To ensure that GSM voice calls are notinterrupted due to LTE data traffic, GSM operations may take priorityover LTE operations. To ensure that operations such as monitoring a GSMpaging channel for incoming paging signals do not unnecessarily disruptLTE operations, control circuitry 42 can, whenever possible, configurethe wireless circuitry of UE 106 so that wireless resources are sharedbetween LTE and GSM functions.

When a user has an incoming GSM call, the GSM network may send UE 106 apaging signal (sometimes referred to as a page) on the GSM pagingchannel using base station 102. When UE 106 detects an incoming page, UE106 can take suitable actions (e.g., call establishment procedures) toset up and receive the incoming GSM call. Pages are typically sentseveral times at fixed intervals by the network, so that devices such asUE 106 will have multiple opportunities to successfully receive a page.

Proper GSM page reception may require that the wireless circuitry of UE106 be periodically tuned to the GSM paging channel, referred to as atune-away operation. If the transceiver circuitry 60 fails to tune tothe GSM paging channel or if the GSM protocol stack 72 in basebandprocessor 58 fails to monitor the paging channel for incoming pages, GSMpages will be missed. On the other hand, excessive monitoring of the GSMpaging channel may have an adverse impact on an active LTE data session.Embodiments of the invention may comprise improved methods for handlingtune-away operations, as described below.

In some embodiments, in order for the UE 106 to conserve power, the GSMand LTE protocol stacks 72 and 74 may support idle mode operations.Also, one or both of the protocol stacks 72 and 74 may support adiscontinuous reception (DRX) mode and/or a connected discontinuousreception (CDRX) mode. DRX mode refers to a mode which powers down atleast a portion of UE circuitry when there is no data (or voice) to bereceived. In DRX and CRDX modes, the UE 106 synchronizes with the basestation 102 and wakes up at specified times or intervals to listen tothe network. DRX is present in several wireless standards such as UMTS,LTE (Long-term evolution), WiMAX, etc. The terms “idle mode”, “DRX” and“CDRX” are explicitly intended to at least include the full extent oftheir ordinary meaning, and are intended to encompass similar types ofmodes in future standards.

Resolving Conflict Between Measurement of a First RAT and Paging of aSecond RAT

As discussed above, a UE may use a single radio (e.g., having a singletransmit chain and a single receive chain) to communicate using twodifferent RATs. For example, the UE may use a single radio tocommunicate using a first RAT and may periodically tune away in order toperform various actions for a second RAT, such as page decoding,measurement, synchronization, etc. Note that the radio may be the singlecellular radio for the UE or may be one of a plurality of cellularradios. In a multiple radio embodiment, and one of the cellular radiosmay be used for time-sharing of the first RAT and the second RAT, e.g.,while the other cellular radio is disabled, such as for powerconsumption reasons, or is used for other purposes. Additionally, the UEmay implement dual SIM dual active (DSDA) and/or dual SIM dual standby(DSDS), as desired.

In one embodiment, the first RAT may be LTE and the second RAT may beGSM or the first RAT may be GSM and the second RAT may be LTE, althoughother combinations of RATs are envisioned. In some cases, it may betypical to tune away periodically in order to perform variousoperations, such as for page decoding and/or synchronization for thesecond RAT (e.g., for neighboring base stations of the current basestation of the second RAT). In the following, the first RAT may bedescribed as LTE and the second RAT may be described as GSM, but any ofthese descriptions may apply to other RATs, as desired.

In comparison to CDMA 2000 1×, SRLTE for GSM may have significantdifferences. For example, GSM tune-away (e.g., for page decoding) may be10 times more frequent (e.g., at least once per 470 ms) than 1× tune-waywhich is generally once per 5.21 s. Additionally, in most cases, theduration of each GSM tune-away may be very short, e.g., 10-20milliseconds, while in most cases duration of 1× tune-away may be 90-100milliseconds.

Due to the nature of frequent GSM tune-aways, the possibility oftune-away requests occurring during an un-interruptible LTE operationmay be high. For example, in LTE connected mode, a measurement gap maybe 6 ms long and may be used for searching/measuring inter-frequency LTEcells and inter-RAT cells, among other possibilities. In some cases, ittakes about 15-21 ms to complete an entire measurement gap operation,e.g., including gap setup time (e.g., for preparing radio frequencyscript for the frequency to be tuned and tune-back from and to thecurrent frequency, and actual radio frequency configuration and radiofrequency tuning), collection of radio frequency samples, and radiofrequency configuration and radio frequency tune-back. In some cases, ifa GSM tune-away request happens during these measurement gap operations,the GSM tune away may be delayed until measurement gap operationsfinish. However, since GSM page detection is only 10 ms, such a delaywould typically lead to missing a GSM page.

Accordingly, to speed up the response time to the GSM tune-away request,and also to minimize impact on LTE performance, one or more of thefollowing embodiments may be implemented.

For example, if a GSM tune-away request occurs prior to the start of theLTE measurement gap, GSM tune-away may take higher priority, and thesame measurement gap may be used for performing the GSM tune-way. In oneembodiment, this process may involve preparing a radio frequency scriptfor tune-away to a frequency associated with GSM, and for tuning backfrom that GSM frequency. Accordingly, at the time of the GSM page, theradio frequency circuitry may be tuned to the GSM frequency and GSMsamples may be collected, e.g., to perform page decoding. After, ifthere are inter-frequency and/or inter-RAT cells pendingdetection/measurement for the measurement gap (e.g., for LTE), then theradio frequency circuitry may be tuned directly to the frequency ofinter-frequency LTE cells or inter-RAT cells and measurement for LTE maybe performed. In this case, the radio may not tune to the normal,serving frequency (e.g., for data communications of LTE) and then to themeasurement frequency, but instead may tune directly to the measurementfrequency. After measurement, the radio may be tuned back to the servingfrequency of LTE for normal operation.

In another case, the GSM tune-away request may occur during themeasurement gap of LTE. In one embodiment, the GSM tune-away may bescheduled right after inter-frequency and/or inter-RAT sample collectionis complete. In particular, instead of tuning back to the LTE servingfrequency, the radio may be directly tuned to the GSM frequency, e.g.,to collect GSM page frame samples. After collecting enough GSM samples,the radio may be tuned back to the LTE serving frequency, e.g., asnormal measurement gap completion.

Thus, in one embodiment, for scenarios of LTE measurement gap collisionwith GSM tune-way (e.g., for paging), the GSM tune away may be insertedbefore or after tuning to the inter frequency and/or inter-RAT frequencyas part of measurement gap. As a result, interruption to LTE normalreception and transmission may be minimized because the network normallyschedules less grant/MCS around the measurement gap and accordingly, GSMtune-way around this measurement gap may result in less impact on LTEthroughput performance. Additionally, a normal schedule ofinter-frequency and/or inter-RAT cell detection and measurement may bemaintained. As an additional benefit, GSM tune-away may occur back toback with measurement gap which may eliminate an extra radio frequencycircuitry tuning overhead.

FIG. 6—Resolving Conflict Between Tune Aways of a First and Second RAT

FIG. 6 is a flowchart diagram illustrating a method for resolvingconflicts between tune aways for a first RAT and a second RAT. Themethod may be performed by a UE device (such as UE 106) that uses afirst radio for both a first RAT and a second RAT (e.g., LTE and GSM,although other combinations of RATs are envisioned). The method shown inFIG. 6 may be used in conjunction with any of the systems or devicesshown in the above Figures, among other devices. In various embodiments,some of the method elements shown may be performed concurrently, in adifferent order than shown, or may be omitted. Note also that additionalmethod elements may also be performed as desired. The method may beperformed as follows.

As shown, in 602, the UE may determine if a tune away of a first RAT(e.g., for measurement, such as inter-cell measurement, inter-RATmeasurement, and/or other measurements) will conflict with a tune awayof a second RAT (e.g., for page decoding). The determination of thisconflict may occur prior to either of the tune aways, or after one hasbeen started, depending on the situation. For example, in an embodimentthat may be particularly applicable to FIG. 6, this determination mayoccur while the tune away for the first RAT has already started. Forexample, the UE may perform measurement (e.g., LTE measurement) for thefirst RAT and may need to perform a page decoding for the second RAT(e.g., page decoding for GSM) after this measurement process hasstarted.

In 604, if the determination of 602 indicates a conflict, then the UEmay tune the first radio from a first frequency of the first RAT (e.g.,a serving frequency) to a second frequency of the first RAT (e.g., forperforming measurement), e.g., instead of to a frequency of the secondRAT to perform the tune away operations of the second RAT. In oneembodiment, the UE may collect samples, e.g., from a serving basestation or neighboring base station of the first RAT.

In 606, after tuning to the second frequency of the first RAT, e.g., forperforming measurement associated with the first RAT, the first radiomay be tuned to a first frequency of the second RAT for the tune awayprocedure of the second RAT (e.g., to perform page decoding associatedwith the second RAT). In one embodiment, the tuning to the firstfrequency of the second RAT from the second frequency of the first RATmay be performed directly, without tuning to any intermediate frequency,such as the first frequency of the first RAT.

In some embodiments, the UE may “pipeline” collection of samples anddecoding of those samples. For example, if samples are collected in 604,e.g., for performing measurement of the first RAT, they may be decodedduring 606 or 608 rather than completing the decoding before moving onto tuning to the frequency of the second RAT and performing theassociated tune away procedure.

In 608, after completing the tune away procedure for the second RAT, theUE may tune the first radio back to the first RAT, e.g., to the firstfrequency (which may be the serving frequency) of the first RAT.

FIGS. 7A and 7B

FIGS. 7A and 7B illustrate an exemplary diagram corresponding to oneembodiment of the method of FIG. 6. In particular, FIGS. 7A and 7Billustrate a case where the tune away request of the second RAT isreceived during a tune away operation of the first RAT. In particular,in FIG. 7A the UE has performs a tune away from for the first RAT from afirst frequency (F0, e.g., the serving frequency of the first RAT) to asecond frequency (F1, e.g., for inter-cell measurement of the firstRAT). A tune away request for the second RAT (e.g., for page decoding)is received while the radio of the UE is tuned to the second frequency(F1). In FIG. 7A, the radio is tuned back to the first frequency of thefirst RAT (F0) and then tuned to the frequency of the second RAT for thetune away operation (F3). After completing the tune away operation, theradio is tuned back to F0.

In contrast, in FIG. 7B, instead of tuning back to F0 between the secondfrequency of the first RAT (F1) and the frequency of the second RAT(F3), the radio is tuned directly from the second frequency of the firstRAT (F1) to the frequency of the second RAT (F3). As shown, in FIG. 7B,the tune away operation of the second RAT is able to be performed soonerthan in FIG. 7A.

FIG. 8—Resolving Conflict Between Tune Aways of a First and Second RAT

FIG. 8 is a flowchart diagram illustrating a method for resolvingconflicts between tune aways for a first RAT and a second RAT. Themethod may be performed by a UE device (such as UE 106) that uses afirst radio for both a first RAT and a second RAT (e.g., LTE and GSM,although other combinations of RATs are envisioned). The method shown inFIG. 8 may be used in conjunction with any of the systems or devicesshown in the above Figures, among other devices. In various embodiments,some of the method elements shown may be performed concurrently, in adifferent order than shown, or may be omitted. Note also that additionalmethod elements may also be performed as desired. The method may beperformed as follows.

As shown, in 802, the UE may determine if a tune away of a first RAT(e.g., for measurement, such as inter-cell measurement, inter-RATmeasurement, and/or other measurements) will conflict with a tune awayof a second RAT (e.g., for page decoding). The determination of thisconflict may occur prior to either of the tune aways, or after one hasbeen started. For example, in an embodiment that may be particularlyapplicable to FIG. 8, this determination may occur prior to thebeginning of tune away for the first RAT. For example, the UE mayreceive a request to perform a tune away for the second RAT (e.g., forperforming page decoding for GSM) prior to beginning a tune away for thefirst RAT (e.g., for performing LTE measurement).

In 804, if the determination of 802 indicates a conflict, then the UEmay tune the first radio from a first frequency of the first RAT (e.g.,a serving frequency) to a first frequency of the second RAT (e.g., forperforming page decoding). In one embodiment, the UE may collect samplesfrom the first frequency of the second RAT (e.g., to detect a page forthe UE).

In 806, after tuning to the first frequency of the second RAT, e.g., forperforming page decoding, the radio may be tuned to a second frequencyof the first RAT for the tune away procedure of the first RAT (e.g., toperform LTE measurement). In one embodiment, the tuning to the secondfrequency of the first RAT from the first frequency of the second RATmay be performed directly, without tuning to any intermediate frequency,such as the first frequency of the first RAT.

In some embodiments, the UE may “pipeline” collection of samples anddecoding of those samples. For example, if samples are collected in 604,e.g., for performing page decoding of the second RAT, they may bedecoded (e.g., or used for detection of the paging) during 606 or 608rather than completing the decoding or detection before moving on totuning to the frequency of the first RAT and performing the associatedtune away procedure.

In 808, after completing the tune away procedure for the first RAT, theUE may tune the first radio back to the first RAT, e.g., to the firstfrequency (which may be the serving frequency) of the first RAT.

FIGS. 9A and 9B

FIGS. 9A and 9B illustrate an exemplary diagram corresponding to oneembodiment of the method of FIG. 8. In particular, FIGS. 9A and 9Billustrate a case where the tune away request of the second RAT isreceived prior to a tune away operation of the first RAT. In particular,in FIG. 9A, the tune away for the second RAT is delayed. In particular,the UE performs a tune away from for the first RAT from a firstfrequency (F0, e.g., the serving frequency of the first RAT) to a secondfrequency (F1, e.g., for inter-cell measurement of the first RAT). Then,in FIG. 7A, the radio is tuned back to the first frequency of the firstRAT (F0) and then tuned to the frequency of the second RAT for the tuneaway operation (F3). After completing the tune away operation, the radiois tuned back to F0.

In contrast, in FIG. 7B, instead of performing the tune away operationof the first RAT, the tune away operation of the second RAT isperformed. In particular, the tune away request is received prior totuning to F1 for the first RAT tune away operation. Accordingly, thetune away operation of the second RAT is performed first, where theradio is tuned from the first frequency of the first RAT (F0) to thefrequency of the second RAT for the tune away operation (F3). Then,instead of tuning back to the first frequency of the first RAT, theradio is tuned directly to the second frequency of the first RAT (F2) toperform the tune away operation of the first RAT. After completion ofthe tune away operation of the first RAT, the radio is tuned back to thefirst frequency of the first RAT (F0).

Inserting Page Decoding of a Second RAT in Measurement for a First RAT

As discussed above, a UE may use a single radio (e.g., having a singletransmit chain and a single receive chain) to communicate using twodifferent RATs. For example, the UE may use a single radio tocommunicate using a first RAT and may periodically tune away in order toperform various actions for a second RAT, such as page decoding,measurement, synchronization, etc. Note that the radio may be the singlecellular radio for the UE or may be one of a plurality of cellularradios. In a multiple radio embodiment, one of the cellular radios maybe used for time-sharing of the first RAT and the second RAT, e.g.,while the other radio sleeps or is used for other purposes.Additionally, the UE may implement dual SIM dual active (DSDA) and/ordual SIM dual standby (DSDS), as desired.

In one embodiment, the first RAT may be LTE and the second RAT may beGSM or the first RAT may be GSM and the second RAT may be LTE, althoughother combinations of RATs are envisioned. In some cases, it may betypical to tune away periodically in order to perform synchronizationfor the second RAT (e.g., for neighboring base stations of the currentbase station of the second RAT). In the following, the first RAT may bedescribed as LTE and the second RAT may be described as GSM, but any ofthese descriptions may apply to other RATs, as desired.

In comparison to CDMA 2000 1×, SRLTE for GSM may have significantdifferences. For example, GSM tune-away (e.g., for page decoding) may be10 times more frequent (e.g., at least once per 470 ms) than 1× tune-waywhich is once per 5.21 s. Additionally, in most cases, the duration ofeach GSM tune-away may be very short, e.g., 10-20 milliseconds, while inmost cases duration of 1× tune-away may be 90-100 milliseconds.

Due to the nature of frequent GSM tune aways, the possibility of tuneaway requests occurring during an uninterruptable LTE operation may behigh. For example, in LTE idle mode, LTE neighbor cell search and/ormeasurement may be classified as uninterruptible operation. Accordingly,if a GSM tune away request occurs during LTE neighbor cell search and/ormeasurement (e.g., for GSM page decoding), the tune away for GSM may bedelayed approximately 30 ms until the measurement operation is complete.While this may be acceptable for a 1× tune away case, it may result in ahigher GSM page miss rate due to the short duration of GSM paging.

Accordingly, to reduce GSM page miss rate due to uninterruptible LTEsearching and/or measurement activity that may deny GSM tune-awayrequest in LTE idle mode, LTE search and/or measurement may be furtherdivided into smaller atomic operations at different stages. Inparticular, since GSM tune away duration may be very small (e.g., about10-20 ms), it may be added between LTE search and/or measurement stageswithout degrading LTE performance significantly.

In LTE idle mode, neighbor cell search may include intra cell search,inter-frequency cell search, and inter-RAT cell search. Intra cellsearch may include serving cell sample collection on half frame andPSS/SSS (primary synchronization signal/secondary synchronizationsignal) detection within it. Inter-frequency cell search may includemultiple cycles of tuning on inter-frequency, inter-frequency cellsample collection on half frame, and PSS/SSS detection within it.Inter-RAT cell search may include multiple cycles of tuning on inter-RATfrequencies, inter-RAT cell sample collection, and inter-RAT cellsignature search within it.

In one embodiment, if a GSM tune away request occurs in the middle ofLTE neighbor cell search, the GSM tune away may be inserted just beforenext intra/inter-frequency/inter-RAT frequency tuning. For example, ifthe GSM tune-away request happens on tuning on inter-frequency F1 forfrequency F1 cell search, after sample collection is completed onfrequency F1, the radio frequency circuitry can be tuned to the GSMfrequency to collect GSM samples (e.g., for page decoding), while in themeantime, inter-frequency F1 cell search can be performed on thecollected samples on frequency F1. When GSM sample collection iscomplete, the radio frequency circuitry can be tuned to nextinter-frequency F2 to collect samples on F2, while GSM samples can bepassed to GSM for GSM page decoding. This embodiment may effectivelymake the GSM tune-away as part of the cell search procedure, e.g., withthe only difference being that the GSM samples collected by GSM tuneaway are used for GSM page decoding, instead of normal cell signaturedetection.

In one embodiment, in LTE idle mode, neighbor cell measurement mayinclude intra cell measurement, inter-frequency cell measurement, andinter-RAT cell measurement. Each type of measurement may include radiofrequency tuning on the related frequency and collection of samples,followed by measuring the reference signal power/energy within thesamples. A GSM tune away can be inserted just before the next radiofrequency tuning for related measurement frequency, instead of delayinguntil entire measurement operation is completed for LTE. For example,measurement of cells of frequency F1 for LTE with a GSM tune-away onFrequency F3 can be inserted just before tune to F2 for LTE, e.g.,F1->F3 (GSM)->F2. This embodiment may effectively make the GSM tune awayas part of the cell measurement procedure for LTE (e.g., in response tothe GSM paging occurring within the measurement operation), except thatGSM samples collected by GSM tune away may be used for GSM pagedecoding, instead of normally for cell reference signal measurement. Thefollowing frequency patterns are exemplary only: F0->F3 (GSM)->F1->F2(e.g., if GSM comes in before F1 is tuned or cancel F1 for F3 and resumeF1 after F3), F0->F1->F3 (GSM)->F2 (e.g., if GSM comes in after F1 isalready tuned or in cases where F1 is completed and GSM is insertedafter completion).

A GSM tune away may occur during intra-cell LTE measurement. Forexample, the radio may be tuned to the serving cell frequency F0 whileperforming intra-cell LTE measurement when the GSM request occurs. Inone embodiment, the radio may immediately tune to GSM to perform GSMprocedures (e.g., page decoding) and then may tune back to F0 in orderto complete intra-cell LTE measurement. Alternatively, after completingGSM procedures, the radio may be tuned to F1 of LTE to performinter-cell or inter-RAT measurements, instead of returning to F0, asdesired. In this case, the radio may be later tuned back to F0 tocomplete intra-cell measurement, if desired. The following frequencypatterns are exemplary only: F0->F3 (GSM)->F0->F1->F2->etc.; F0->F3(GSM)->F1->F2-> . . . F0; F3 (GSM)->F0->F1->F2->etc.

These embodiments may result in reduction of GSM tune away max delaydown to about 5 ms, which may be used to collect LTE half frame samples.These embodiments may dramatically reduce GSM page miss rate due todenying a GSM tune away when cell search and/or measurement is on-goingfor LTE.

FIG. 10—Inserting Tune Away of a Second RAT in Intra-Cell Measurementfor a First RAT

FIG. 10 is a flowchart diagram illustrating a method for inserting pagedecoding (or other procedures) of a second RAT within measurement of afirst RAT. The method of FIG. 10 may be performed by a UE device (suchas UE 106) that uses a first radio for both the first RAT and the secondRAT (e.g., LTE and GSM, although other combinations of RATs areenvisioned). The method shown in FIG. 9 may be used in conjunction withany of the systems or devices shown in the above Figures, among otherdevices. In various embodiments, some of the method elements shown maybe performed concurrently, in a different order than shown, or may beomitted. Note also that additional method elements may also be performedas desired. The method may be performed as follows.

In 1002, the UE may perform intra-cell measurement operations at a firstfrequency of the first RAT. For example, the UE may wake from idle modeand may operate at the first frequency in a first cell of the first RATand then may perform intra-cell measurement of the first RAT.

In 1004, the UE may receive a request to perform tune-away to afrequency of the second RAT, e.g., while the UE is tuned to the firstfrequency of the first RAT to perform intra-cell measurement operations.The request may be received prior to completion of the intra-cellmeasurement operations of the first RAT.

In 1006, in response to the tune-away request from the second RAT, theUE may perform the tune-away operations for the second RAT. Morespecifically, the UE may tune the first radio from the first frequencyof the first RAT to a frequency of the second RAT in order to performthe tune-away operation (e.g., page decoding for the second RAT). Insome embodiments, the tune-away operations may include gathering samplesfor the frequency of the second RAT and then performing searching oranalysis of those samples. In some embodiments, the UE may immediatelytune away to the frequency of the second RAT in response to thetune-away request (e.g., without any substantial delay). Alternatively,the UE may introduce a small delay, e.g., if samples are still beingcollected, such as in cases where the sample collection is almostcomplete.

In 1008, after 1006, the intra-cell measurement operations for the firstRAT may be completed. In some embodiments, completion of the intra-cellmeasurement operations may be performed immediately after the tune-awayoperations of the first RAT. Alternatively, after the tune-awayoperation of the first RAT, other measurement operations (e.g.,inter-cell or inter-RAT) may be performed for the first RAT. Forexample, instead of tuning back to the first frequency (e.g., theserving frequency) of the first RAT after the tune away operation of thesecond RAT, the radio of the UE may be tuned to a second frequency ofthe first RAT, e.g., for performing inter-cell measurements. After theseother measurement operations, the radio may be tuned back to the firstfrequency to complete intra-cell measurements.

In some embodiments, the gathering of samples (e.g., for the variousmeasurements of the first RAT and/or the tune-away operation of thesecond RAT) and analysis of those gathered samples may be pipelined. Forexample, samples may be gathered for a frequency and immediately theradio may be tuned to a new frequency to gather additional sampleswhile, at the same time, the samples for the prior frequency areanalyzed, thus increasing efficiency of the overall process.

FIGS. 11A and 11B

FIGS. 11A and 11B illustrate an exemplary diagram corresponding to oneembodiment of the method of FIG. 10. In particular, FIGS. 11A and 11Billustrate a case where the tune away request of the second RAT isreceived during intra-cell measurements for the first RAT.

In particular, as shown in FIG. 11A, the UE is initially in idle mode,and then tunes to the serving frequency of the first RAT (F0). In theserving frequency, the UE may perform intra-cell measurements. Duringthis time, the UE receives a tune away request of the second RAT. Inthis case, the UE completes intra-cell measurement and continues on toperform inter-cell and/or inter-RAT measurement in frequencies F1 andF2. After, the UE tunes back to the serving frequency of the first RAT(F0) and then tunes to F3 for performing the tune away operation of thesecond RAT.

In FIG. 11B, a similar situation is shown. However, in FIG. 11B, whenthe tune away request is received for the second RAT, the UE tunes theradio from the serving frequency of the first RAT to the frequency ofthe second RAT (F3) in order to perform the tune away operation (e.g.,page decoding). Then, the UE tunes the radio directly to F1 followed byF2 to perform the inter-cell and/or inter-RAT measurement for the firstRAT. The UE can then tune back to F0, e.g., to complete the intra-cellmeasurement of the first RAT.

FIG. 12—Inserting Tune Away of a Second RAT in Inter-Cell and/orInter-RAT Measurement for a First RAT

FIG. 12 is a flowchart diagram illustrating a method for inserting pagedecoding (or other procedures) of a second RAT within measurement of afirst RAT. The method of FIG. 12 may be performed by a UE device (suchas UE 106) that uses a first radio for both the first RAT and the secondRAT (e.g., LTE and GSM, although other combinations of RATs areenvisioned). The method shown in FIG. 9 may be used in conjunction withany of the systems or devices shown in the above Figures, among otherdevices. In various embodiments, some of the method elements shown maybe performed concurrently, in a different order than shown, or may beomitted. Note also that additional method elements may also be performedas desired. The method may be performed as follows.

In 1202, the UE may perform inter-cell measurement and/or inter-RAToperations for a first RAT. Performing inter-cell and/or inter-RATmeasurement operations may include repeatedly performing measurementoperations on different frequencies of the first RAT by: tuning thefirst radio to a new frequency of the first RAT (e.g., corresponding toa neighboring cell of the first RAT) and performing measurements on thatnew frequency of the first RAT. Inter-cell and/or inter-RAT measurementoperations may be performed for a plurality of frequencies, e.g.,including a first frequency (e.g., “F1”), a second frequency (e.g.,“F2”), etc. For inter-cell measurements, each of these frequencies maybe associated with the first RAT, e.g., base stations of the first RAT.

In 1204, the UE may receive a request to perform tune-away to afrequency of the second RAT, e.g., while the UE is tuned to a frequencyof the plurality of frequencies of 1102. For example, the request may beto perform page decoding for the second RAT.

In 1206, in response to the tune-away request from the second RAT, theUE may perform the tune-away operations for the second RAT. Morespecifically, the UE may tune the first radio from the current frequencyof the plurality of frequencies associated with the measurementoperations of the first RAT to a frequency of the second RAT in order toperform the tune-away operation of the second RAT (e.g., page decodingfor the second RAT). In some embodiments, the tune-away operations mayinclude gathering samples for the frequency of the second RAT and thenperforming searching or analysis of those samples. In some embodiments,the UE may immediately tune away to the frequency of the second RAT inresponse to the tune-away request (e.g., without any substantial delay).Alternatively, the UE may introduce a small delay, e.g., if samples arestill being collected, such as in cases where the sample collection isalmost complete.

In 1208, after 1206, the UE may continue performing inter-cellmeasurements. More specifically, the UE may tune the first radio fromthe frequency of the second RAT to one of the plurality of frequenciesfor performing measurements associated with the first RAT. In oneembodiment, the UE may tune the first radio to the frequency that wastuned away from in 1206 (e.g., if measurement was not completed for thatfrequency). Alternatively, the UE may tune the first radio to a nextfrequency of the plurality of frequencies to continue performingmeasurements associated with the first RAT (e.g., if the previousfrequency was already completed and/or if it was not, but completing thefrequency did not need to occur and/or could be completed at a latertime).

Similar to discussions above, in some embodiments, the gathering ofsamples (e.g., for the various measurements of the first RAT and/or thetune-away operation of the second RAT) and analysis of those gatheredsamples may be pipelined. For example, samples may be gathered for afrequency and immediately the radio may be tuned to a new frequency togather additional samples while, at the same time, the samples for theprior frequency are analyzed, thus increasing efficiency of the overallprocess.

FIGS. 13A and 13B

FIGS. 13A and 13B illustrate an exemplary diagram corresponding to oneembodiment of the method of FIG. 12. In particular, FIGS. 13A and 13Billustrate a case where the tune away request of the second RAT isreceived during inter-cell and/or inter-RAT measurements for the firstRAT.

In particular, as shown in FIG. 11A, the UE is initially in idle mode,and then tunes to the serving frequency of the first RAT (F0). The UEthen begins inter-cell and/or inter-RAT measurements at frequency F1 forthe first RAT. While tuned to F1, the UE receives a tune away request ofthe second RAT. In this case, the UE completes inter-cell and/orinter-RAT measurement in frequencies F1 and F2. After, the UE tunes backto the serving frequency of the first RAT (F0) and then tunes to F3 forperforming the tune away operation of the second RAT.

In FIG. 11B, a similar situation is shown. However, in FIG. 11B, whenthe tune away request is received for the second RAT while tuned to F1,the UE tunes the radio from F1 of the first RAT to the frequency of thesecond RAT (F3) in order to perform the tune away operation (e.g., pagedecoding). Then, the UE tunes the radio directly to F2 to continue toperform the inter-cell and/or inter-RAT measurement for the first RAT.The UE can then tune back to F0.

In the example of FIG. 11B, the UE may have received enough samples inF1 to be able to perform detection on the samples while tuning to F3 forthe second RAT, e.g., following the pipelining embodiments discussedabove.

Inserting Page Decoding of a Second RAT in Warm Up for a First RAT

As discussed above, a UE may use a single radio (e.g., having a singletransmit chain and a single receive chain) to communicate using twodifferent RATs. For example, the UE may use a single radio tocommunicate using a first RAT and may periodically tune away in order toperform various actions for a second RAT, such as page decoding,measurement, synchronization, etc. Note that the radio may be the singlecellular radio for the UE or may be one of a plurality of cellularradios. In a multiple radio embodiment, and one of the cellular radiosmay be used for time-sharing of the first RAT and the second RAT, e.g.,while the other radio is asleep or used for other purposes.Additionally, the UE may implement dual SIM dual active (DSDA) and/ordual SIM dual standby (DSDS), as desired.

In one embodiment, the first RAT may be LTE and the second RAT may beGSM or the first RAT may be GSM and the second RAT may be LTE, althoughother combinations of RATs are envisioned. In some cases, it may betypical to tune away periodically in order to perform measurement and/orsynchronization for the second RAT (e.g., for neighboring base stationsof the current base station of the second RAT). In the following, thefirst RAT may be described as LTE and the second RAT may be described asGSM, but any of these descriptions may apply to other RATs, as desired.

In comparison to CDMA 2000 1×, SRLTE for GSM may have significantdifferences. For example, GSM tune-away (e.g., for page decoding) may be10 times more frequent (e.g., at least once per 470 ms) than 1× tune-waywhich is once per 5.21 s. Additionally, in most cases, the duration ofeach GSM tune-away may be very short, e.g., 10-20 milliseconds, while inmost cases duration of 1× tune-away may be 90-100 milliseconds.

CDRX (e.g., in LTE connected mode) provides fast data access responsetime while conserving power by going to sleep whenever there are notransmissions (e.g., data transmissions). A typical CDRX cycle for LTEis 320 ms. Additionally, as mentioned above, GSM tune-aways are fairlyfrequent (e.g., once per 470 ms). As a result, it is fairly likely thata GSM tune-away request may occur during an LTE CDRX wakeup period,which include crystal oscillator warm up, radio frequency chainconfiguration, and Time/Frequency Tracking loop (TTL/FTL) warm up. ThisCDRX wakeup period normally takes 17 ms to 25 ms (e.g., including radiofrequency circuitry warm up-8 ms, TTL/FTL warm up 8 ms-17 ms, and radiofrequency configuration 2-3 ms) which is a long enough to cause GSM tomiss a potential page during page decoding if the GSM tune-away isdelayed.

The following embodiments may resolve or minimize this issue.

Crystal oscillator warm up is common for either LTE wakeup or GSMwakeup. Additionally, radio frequency chain configuration for LTE isalso needed for creating a tune-back radio frequency script which, whenexecuted, may reconfigure only the difference between LTE and GSM radiofrequency configuration for the radio frequency chain interface, e.g.,so that tune-back from GSM to LTE takes minimal time.

TTL/FTL warm up may be used for re-verification of LTE time trackingerror and frequency tracking error due to sleep. Although it may benecessary for LTE transmission and receiving at correct timing andfrequency after wakeup, it can be delayed until after the GSM tune-away.Accordingly, if the GSM tune-away request happens during radio frequencywarm up and radio frequency configuration, the radio frequency warm upand configuration can be delayed until it is completed. In another case,if GSM tune away request happens during TTL/FTL warm-up, the TTL/FTLwarm-up can be cancelled and the radio frequency circuitry can beimmediately tuned to GSM frequency to collect GSM samples and start GSMprocessing, such as page decoding.

Accordingly, when the radio frequency circuitry is tuned back from GSM,LTE TTL/FTL warm-up procedure can be restarted, and LTE transmission andreceiving then can be resumed after TTL/FTL warm-up completes.

By implementing these embodiments, fewer GSM page may be missed whileLTE performance degradation may be minimized.

FIG. 14—Inserting Tune Away of a Second RAT in Warm Up for a First RAT

FIG. 14 is a flowchart diagram illustrating a method for inserting pagedecoding (or other procedures) of a second RAT within warm up of a firstRAT. The method of FIG. 14 may be performed by a UE device (such as UE106) that uses a first radio for both the first RAT and the second RAT(e.g., LTE and GSM, although other combinations of RATs are envisioned).The method shown in FIG. 13 may be used in conjunction with any of thesystems or devices shown in the above Figures, among other devices. Invarious embodiments, some of the method elements shown may be performedconcurrently, in a different order than shown, or may be omitted. Notealso that additional method elements may also be performed as desired.The method may be performed as follows.

In 1402, the UE may begin waking up from a sleep mode to operate in afirst RAT. The UE may have been in a sleep mode for the first RAT,circuitry associated with the first RAT, the first radio or radiofrequency circuitry of the first radio, the UE in general, and/or otherportions or components of the UE, as desired. Generally, immediatelyprior to waking up in 1402, the UE may not have been actively using thefirst radio to perform communication using the first RAT.

The wake up procedure of 1402 may include one or more of performing acrystal oscillator warm up (e.g., providing power to the crystaloscillator and wait for it to warm up and/or stabilize), performingradio frequency circuitry warm up, performing start-up operations of aprocessor (e.g., a CPU) of the UE, and/or performing tracking loopoperations (such as time tracking loop and/or frequency tracking loopoperations) to synchronize operations with a base station of the firstRAT. In one embodiment, the crystal oscillator may be used for operatinga first clock that may be used for communication using the first RAT.

In 1404, during the warm up procedure of 1402, a tune away request maybe received for the second RAT, e.g., to perform page decoding for thesecond RAT.

In 1406, in response to the tune away request in 1404, the tune awayoperation may be performed. For example, the first radio of the UE maybe tuned to a frequency of the second RAT to perform the tune awayoperation (e.g., page decoding).

However, the timing of the receipt of the tune away request with respectto the wake up procedures may affect when the tune away operation isperformed. For example, if the tune away request is received prior toperforming the timing loop operations (e.g., during crystal oscillatorwarm up, radio frequency circuitry warm up, and/or start-up operationsof the processor), then the tune away operation may be performed afterstart-up operations of the CPU and prior to the timing loop operations.However, if the tune away request is received during the timing loopoperations, then the timing loop operations may be cancelled, and thetune away operation of the second RAT may be performed. In this case,the timing loop operations may be completed or restarted after the tuneaway operation of the second RAT.

In 1408, after performing the tune away operation in 1306, the wake upprocedure of 1402 may be completed. In particular, in 1408, the timingloop operations of the wake up procedure of 1402 may be performed.

Embodiments of the present invention may be realized in any of variousforms. For example, in some embodiments, the present invention may berealized as a computer-implemented method, a computer-readable memorymedium, or a computer system. In other embodiments, the presentinvention may be realized using one or more custom-designed hardwaredevices such as ASICs. In other embodiments, the present invention maybe realized using one or more programmable hardware elements such asFPGAs.

In some embodiments, a non-transitory computer-readable memory mediummay be configured so that it stores program instructions and/or data,where the program instructions, if executed by a computer system, causethe computer system to perform a method, e.g., any of a methodembodiments described herein, or, any combination of the methodembodiments described herein, or, any subset of any of the methodembodiments described herein, or, any combination of such subsets.

In some embodiments, a device (e.g., a UE) may be configured to includea processor (or a set of processors) and a memory medium, where thememory medium stores program instructions, where the processor isconfigured to read and execute the program instructions from the memorymedium, where the program instructions are executable to implement anyof the various method embodiments described herein (or, any combinationof the method embodiments described herein, or, any subset of any of themethod embodiments described herein, or, any combination of suchsubsets). The device may be realized in any of various forms.

Although the embodiments above have been described in considerabledetail, numerous variations and modifications will become apparent tothose skilled in the art once the above disclosure is fully appreciated.It is intended that the following claims be interpreted to embrace allsuch variations and modifications.

What is claimed is:
 1. An apparatus, comprising: one or more processingelements, wherein the one or more processing elements are configured foroperation within a user equipment device (UE) comprising a first radio,wherein the first radio is configurable to operate according to a firstradio access technology (RAT) and a second RAT, wherein the one or moreprocessing elements are configured to: wake from an idle mode andoperating at a first frequency of the first RAT; perform measurementoperations at the first frequency of the first RAT using the firstradio; receive a tune-away request from the second RAT during saidperforming the measurement operations at the first frequency of thefirst RAT; and perform tune-away operations of the second RAT using thefirst radio in response to receiving the tune-away request from thesecond RAT, wherein said performing the tune-away operations of thesecond RAT comprises tuning the first radio from the first frequency ofthe first RAT to a frequency of the second RAT, wherein said performingthe tune-away operations of the second RAT occurs before completion ofthe measurement operations at the first frequency of the first RAT. 2.The apparatus of claim 1, wherein the measurement operations at thefirst frequency of the first RAT comprise intra-cell measurementoperations.
 3. The apparatus of claim 1, wherein the one or moreprocessing elements are further configured to: after said performing thetune-away operations of the second RAT, tune the first radio of the UEfrom the frequency of the second RAT to the first frequency of the firstRAT; and complete the measurement operations at the first frequency inthe first cell of the first RAT after said tuning the first radio of theUE from the frequency of the second RAT to the first frequency of thefirst RAT.
 4. The apparatus of claim 3, wherein said performing thetune-away operations of the second RAT comprises performing pagingoperations on the second RAT to collect paging samples on the secondRAT, wherein the one or more processing elements are further configuredto decode the paging samples of the second RAT concurrently with saidcompleting the measurement operations at the first frequency in of thefirst RAT.
 5. The apparatus of claim 1, wherein the measurementoperations at the first frequency of the first RAT comprise intra-cellmeasurement operations, wherein the method further comprises: after saidperforming the tune-away operations of the second RAT, tuning the firstradio of the UE from the frequency of the second RAT to a secondfrequency of the first RAT; and performing inter-cell measurements onthe second frequency of the first RAT.
 6. The apparatus of claim 5,wherein said performing the tune-away operations of the second RATcomprises performing paging operations on the second RAT to collectpaging samples on the second RAT, and wherein the one or more processingelements are further configured to decode the paging samples of thesecond RAT concurrently with said performing inter-cell measurements onthe second frequency of the first RAT.
 7. The apparatus of claim 1,wherein the one or more processing elements are further configured to:complete the intra-cell measurement operations at the first frequency inthe first cell of the first RAT after said performing inter-cellmeasurements on the second frequency of the first RAT.
 8. The apparatusof claim 1, wherein the first RAT is long term evolution (LTE) and thesecond RAT is global system for mobile communications (GSM).
 9. Theapparatus of claim 1, wherein the UE comprises two smart cards whicheach implement SIM (Subscriber Identity Module) functionality, whereinthe UE implements DSDA (Dual SIM Dual Active) functionality.
 10. Theapparatus of claim 1, wherein the UE comprises the first radio and asecond radio and wherein the second radio is turned off during operationof the method.
 11. An apparatus configured for inclusion in a userequipment device (UE) having a first radio for communicating using afirst radio access technology (RAT) and a second RAT, comprising: one ormore processing elements, wherein the one or more processing elementsare configured to: perform a plurality of measurement operations on thefirst RAT, wherein performing measurement operations on the first RATcomprises, for each measurement operation: tuning the first radio to arespective frequency of the first RAT; and performing the measurementson the respective frequency of the first RAT after said tuning the firstradio to the frequency of the first RAT; receive a tune-away requestrelated to the second RAT, wherein the tune-away request for the secondRAT is received when the radio is tuned to a current frequency of thefirst RAT during said performing the plurality of measurement operationson the first RAT; tune the first radio from the current frequency of thefirst RAT to a frequency of the second RAT in response to receiving thetune-away request from the second RAT; and perform the tune-awayoperations of the second RAT in response to receiving the tune-awayrequest, wherein performing the tune-away operations is performed aftertuning the first radio from the current frequency of the first RAT tothe frequency of the second RAT.
 12. The apparatus of claim 11, whereinthe one or more processing elements are further configured to: afterperforming the tune-away operations of the second RAT, resume performingthe plurality of measurement operations on the first RAT.
 13. Theapparatus of claim 12, wherein performing the tune-away operations ofthe second RAT comprises performing paging operations on the second RATto collect paging samples on the second RAT, wherein the one or moreprocessing elements are further configured to decode the paging samplesof the second RAT concurrently with resuming performing the plurality ofmeasurement operations on the first RAT.
 14. The apparatus of claim 11,wherein receiving the tune-away request from the second RAT occurs priorto completing the measurements on the current frequency of the firstRAT, and wherein tuning the first radio from the current frequency ofthe first RAT to the frequency of the second RAT occurs prior tocompleting the measurements on the current frequency of the first RAT.15. The apparatus of claim 14, wherein the one or more processingelements are further configured to: tune the first radio to a nextfrequency of the first RAT after performing the tune-away operations ofthe second RAT, and resuming performing the measurement operations ofthe first RAT; or tune the first radio back to the current frequency ofthe first RAT after performing the tune-away operations of the secondRAT and complete the measurements on the current frequency of the firstRAT.
 16. A user equipment device (UE), comprising: a first radio,wherein the first radio is configured to perform communication using afirst radio access technology (RAT) and a second RAT and maintain aconnection to both the first RAT and the second RAT; and one or moreprocessors coupled to the first radio, wherein the one or moreprocessors and the first radio are configured to: perform a plurality ofmeasurement operations on the first RAT, wherein performing measurementoperations on the first RAT comprises, for each measurement operation:tuning the first radio to a respective frequency of the first RAT; andperforming the measurements on the respective frequency of the first RATafter said tuning the first radio to the frequency of the first RAT;receive a tune-away request related to the second RAT, wherein thetune-away request for the second RAT is received when the radio is tunedto a current frequency of the first RAT during said performing theplurality of measurement operations on the first RAT; tune the firstradio from the current frequency of the first RAT to a frequency of thesecond RAT in response to receiving the tune-away request from thesecond RAT; and perform the tune-away operations of the second RAT inresponse to receiving the tune-away request, wherein performing thetune-away operations is performed after tuning the first radio from thecurrent frequency of the first RAT to the frequency of the second RAT.17. The UE of claim 16, wherein the one or more processors are furtherconfigured to: after performing the tune-away operations of the secondRAT, resume performing the plurality of measurement operations on thefirst RAT.
 18. The UE of claim 17, wherein performing the tune-awayoperations of the second RAT comprises performing paging operations onthe second RAT to collect paging samples on the second RAT, wherein theone or more processors are further configured to decode the pagingsamples of the second RAT concurrently with resuming performing theplurality of measurement operations on the first RAT.
 19. The UE ofclaim 16, wherein receiving the tune-away request from the second RAToccurs prior to completing the measurements on the current frequency ofthe first RAT, and wherein tuning the first radio from the currentfrequency of the first RAT to the frequency of the second RAT occursprior to completing the measurements on the current frequency of thefirst RAT.
 20. The UE of claim 19, wherein the one or more processorsare further configured to: tune the first radio to a next frequency ofthe first RAT after performing the tune-away operations of the secondRAT, and resuming performing the measurement operations of the firstRAT; or tune the first radio back to the current frequency of the firstRAT after performing the tune-away operations of the second RAT andcomplete the measurements on the current frequency of the first RAT.